The present invention relates to a method of extracting liquid and/or gas from a fluidic or gaseous mixture containing dispersed particles, in which process liquid and/or gas is processed through an oscillating screen or filter surface with the retention of particles. The invention also relates to a device for executing the process, which device normally includes a container receiving a mixture, at least one screening or filter body which has at least the mesh of the size to retain particles, and devices for conducting the processed liquid.
A method and a device of the type under discussion have been disclosed, for example in CH-PS No. 602, 102. The method and device of the reference are intended for retaining solids suspended in liquids. The mixture is processed through the oscillating screening wire basket through which liquid and desired small particles pass whereas the particles which can not pass through the mesh of the basket are retained whereby the vibrations of the screening element, e.g. wire basket must prevent the building up of filter cakes. With such mode of operation, particles of the size smaller than the mesh openings of the screen are not retained on the screen.
With other conventional filtering methods, only such particles can pass through the screening or filtering surface, the size of which is smaller than the mesh size of the filter. Such methods have the disadvantage which resides in that the particles retained on the screen or filter surface are collected under the building of filter cakes whereby they must be practically pushed through the liquid flow into the mesh of the filter and it is required, in relatively short intervals, to remove filter cakes from the filter surface and to free the mesh of the filter. These problems have been solved by different means, for example by a cross flow filtration in which the mixture is fed parallel to the filter surface whereby the liquid flow must float the deposited solids from the filter surface. It has been also suggested to displace the screen or filter surface in rotation so as to release the upper surface of the filter from the coating or overlay. All these measures have only limited the efficiency and are non-suitable for mixtures utilized particularly for many biotechnological purposes for example biocatalysts, microoorganisms, cell cultures, etc., due to high shearing forces.